Refrigerant PT Comparison Tool
Pick 2-4 refrigerants from the dataset; the tool overlays their saturation curves on one chart. Glide visible for zeotropic blends. Useful for retrofit feasibility, new-equipment specification, and commercial low-GWP transition planning.
Solid line = bubble curve, dashed line = dew curve (zeotropic blends only). Charts of refrigerants with very different pressure ranges (e.g. R-744 vs anything else) compress; toggle to log scale support is pending.
What the PT comparison chart actually shows
Each curve on the overlay chart represents one refrigerant's saturation pressure plotted against saturation temperature. At any temperature on the x-axis, you can read off the pressure at which that refrigerant's liquid and vapor coexist in equilibrium. Comparing two curves at the same temperature shows the pressure delta between the refrigerants.
For pure refrigerants and azeotropes (single saturation temperature per pressure), each is a single solid curve. For zeotropic blends, two curves: the bubble line (solid) where the first vapor forms when heating the liquid, and the dew line (dashed) where the last liquid disappears when condensing the vapor. The vertical distance between bubble and dew at any pressure is the glide.
Common comparison presets — what each one reveals
| Use case | Refrigerants to overlay | What to look for |
|---|---|---|
| Residential AC phase-down | R-22 · R-410A · R-32 · R-454B | Pressure envelope trajectory across HCFC → HFC → A2L |
| R-22 retrofit candidates | R-22 · R-407C · R-422D · R-454C | Which retrofit matches R-22 envelope; dew vs bubble for zeotropes |
| Commercial LT low-GWP | R-404A · R-448A · R-449A · R-454C | AIM Act compliance path; capacity match at low-temp evap |
| Mobile AC transition | R-134a · R-1234yf | SAE J639 / EU MAC Directive compatibility |
| Chiller refrigerants | R-134a · R-513A · R-1234ze · R-1233zd | Centrifugal chiller R-134a replacement options |
| High vs low pressure | R-744 · R-410A · R-22 · R-134a | CO₂ trans-critical envelope vs traditional HFC range |
Reading the chart for retrofit feasibility
A successful refrigerant retrofit requires the candidate's pressure envelope to fall within the equipment's design pressure ratings across the full operating range. The PT overlay reveals this at a glance.
Look at three operating temperatures: 40°F (typical evaporator saturation for AC), 70°F (typical room ambient), and 95-110°F (typical condenser saturation). If the candidate curve sits within 10-20% of the incumbent at all three points, the pressure-envelope match is acceptable. Differences greater than 30% require equipment re-rating or replacement.
| Δ pressure at 95°F | Feasibility |
|---|---|
| ±5% | Drop-in compatible (pressure-wise). Verify lubricant + safety class. |
| ±5-20% | Acceptable with standard retrofit (oil change, drier, recharge by weight). |
| ±20-40% | Marginal. Component pressure ratings need re-evaluation; capacity may shift. |
| ±40%+ | Not a drop-in. Equipment redesign or full replacement required. |
Real comparison scenarios — using the chart for decisions
Six scenarios showing how to interpret the PT overlay for specific service or specification decisions. Each maps a comparison to a verdict (compatible, marginal, requires redesign).
Pressure-envelope check for residential R-22 retrofit
Scenario · Legacy R-22 residential AC. Customer wants to extend equipment life rather than full replacement. R-407C is the most common R-22 retrofit option — does the pressure envelope match?
| Temp | R-22 (pure) | R-407C bubble | R-407C dew | Max Δ |
|---|---|---|---|---|
| 40°F evap | 69 PSIG | 80 | 63 | +16% |
| 95°F cond | 181 PSIG | 215 | 180 | +19% |
| 120°F cutout | 260 PSIG | 305 | 258 | +17% |
New equipment specification — R-32 vs R-410A pressure delta
Scenario · Selecting between R-32 and R-410A for new residential AC equipment in the 2026 AIM Act-driven transition. R-32 is the dominant A2L choice in Asia; R-454B leads in North America. Quick pressure check.
| Temp | R-410A | R-32 | Δ vs R-410A |
|---|---|---|---|
| 40°F evap | 119 PSIG | 124 PSIG | +4% |
| 95°F cond | 278 PSIG | 296 PSIG | +6% |
| 120°F cutout | 380 PSIG | 410 PSIG | +8% |
Commercial LT walk-in low-GWP transition
Scenario · Supermarket R-404A walk-in freezer. AIM Act prohibits R-404A in new commercial refrigeration. Comparing R-454C (sub-150 GWP, A2L) as the replacement for new equipment specification.
| Temp | R-404A | R-454C bubble | R-454C dew | Δ at bubble |
|---|---|---|---|---|
| −20°F evap | 19 PSIG | 21 | 5 | +11% |
| 95°F cond | 232 PSIG | 220 | 185 | −5% |
Mobile AC R-134a to R-1234yf — pressure envelope was engineered to match
Scenario · 2017+ vehicle production transitioned from R-134a to R-1234yf for global GWP compliance (EU MAC Directive, US EPA SNAP). R-1234yf was engineered specifically to preserve R-134a-compatible mobile AC equipment design.
| Temp | R-134a | R-1234yf | Δ |
|---|---|---|---|
| 35°F evap | 28 PSIG | 26 PSIG | −7% |
| 100°F cabin ambient | 124 PSIG | 127 PSIG | +2% |
| 140°F engine bay | 217 PSIG | 227 PSIG | +5% |
Centrifugal chiller R-134a replacement — R-513A is the leading option
Scenario · Centrifugal water-cooled chiller, R-134a, due for refrigerant transition (AIM Act, lower GWP). R-513A (Trane / Chemours Opteon XP10) is the most common chiller replacement; it's an azeotropic R-134a/R-1234yf blend.
| Temp | R-134a | R-513A | Δ |
|---|---|---|---|
| 40°F evap | 35 PSIG | 37 PSIG | +6% |
| 110°F cond | 146 PSIG | 157 PSIG | +8% |
| 130°F max ambient | 199 PSIG | 213 PSIG | +7% |
CO₂ transcritical vs HFC sub-critical — different operating regimes
Scenario · Considering R-744 transcritical for a supermarket commercial refrigeration project. Comparing against R-410A and R-22 to visualize the dramatic pressure-envelope difference.
| Temp | R-22 | R-410A | R-744 | R-744 vs R-410A |
|---|---|---|---|---|
| −20°F (LT evap) | 10 PSIG | 26 | 199 | +665% |
| 20°F (MT evap) | 41 PSIG | 78 | 421 | +440% |
| 87.8°F (CO₂ critical) | 157 PSIG | 240 | 1057 | +340% |
| 100°F+ | 196 PSIG | 320 | transcritical | N/A |
What PT comparison alone does NOT tell you
The pressure-envelope match shown by the PT overlay is necessary but not sufficient for retrofit decisions. Other factors that the chart does not show must be evaluated separately:
- Lubricant compatibility. R-22 systems use mineral oil; HFC replacements (R-407C, R-410A) require POE. Hydrocarbon blends (R-422D, R-438A) include small hydrocarbon components specifically to retain mineral-oil compatibility. The PT chart cannot show this.
- Safety classification. A1 (non-flammable, low-toxicity) vs A2L (mildly flammable) vs A3 (flammable) vs B (toxic) shift charge limits, leak detection requirements, and installation procedures. R-32 / R-454B are A2L; R-410A is A1. Same pressure envelope, different safety regime.
- GWP. R-22 (GWP 1810) vs R-407C (GWP 1774) — nearly identical GWP, no climate benefit from retrofit. R-22 vs R-454C (GWP 148) — substantial climate benefit. The PT chart shows pressure, not climate impact.
- Capacity. Pressure envelope match does not guarantee capacity match. R-32 produces ~5% more cooling capacity per unit displacement than R-410A even though pressures are similar — equipment sizing matters.
- Component pressure ratings.Beyond the refrigerant pressure envelope, the system's line set, valves, accumulator, receiver, and compressor have their own pressure ratings. Equipment originally certified for R-22 (500 PSI design) cannot be retrofitted to R-410A or R-744 without re-rating.
When to use this calculator vs the others
- PT Comparison Tool (this page) — quick visual envelope check across 2-4 refrigerants. Best for preliminary retrofit screening, new-equipment specification, and education.
- Retrofit Compatibility — structured pair-comparison covering pressure, lubricant, safety class, glide, GWP, application fit. Use after PT screening to evaluate full feasibility.
- PT Calculator — single-refrigerant lookup, either direction. Use for specific point calculations after deciding on a refrigerant.
- Refrigerant Comparison Guide — long-form sourced reference for all common HVAC refrigerant comparisons.
- Per-refrigerant detail pages — every refrigerant in the dataset has its own page with full PT chart, properties, lubricant, safety classification, and replacement options.
Primary sources
- CoolProp 7.2.0 (Bell, Wronski, Quoilin, Lemort 2014, doi:10.1021/ie4033999) — REFPROP-compatible Helmholtz EOS for all saturation pressures.
- AHRI Standard 700-2019 — refrigerant specifications and cross-reference to CoolProp values.
- ASHRAE Standard 34-2022 — refrigerant designation, safety classification, composition.
- Manufacturer technical datasheets— Honeywell, Chemours, Arkema, AGC PT charts for 11 manufacturer-blend refrigerants not in CoolProp's library (R-448A, R-450A, R-1336mzz(Z), etc.).
- EPA AIM Act (40 CFR Part 84) — phase-down schedule for high-GWP refrigerants driving retrofit and new-equipment decisions.
- SAE J639 / J2912 — mobile AC service procedures for R-134a and R-1234yf.
- EU F-Gas Regulation (517/2014, 2024/573) — European phase-down driving similar refrigerant transitions globally.
How to use this calculator
- Tool starts with R-22, R-410A, R-32, and R-454B — the residential AC phase-down trajectory.
- Swap any refrigerant from the dropdowns. Add up to 4 series, or remove down to 2.
- Toggle units between °F/°C and PSIG/kPa.
- Read curves at your operating points: 40°F evap / 110°F cond for residential AC; -20°F evap / 95°F cond for LT walk-in; 45°F evap / 110°F cond for chiller.
- For zeotropic blends, both bubble (solid) and dew (dashed) curves are shown — the gap is the glide.
Common errors
- Comparing across vastly different pressure envelopes (R-744 + R-1234ze) on one chart — readability suffers. Split into separate comparisons.
- Ignoring glide on zeotropic blends — the wide gap matters for service measurement and capacity calculations.
- Treating curve crossover as significant — at one specific temperature curves can coincide; the broader envelope shape matters more.
- Using PT overlay alone for retrofit decisions — lubricant compatibility, safety class, and GWP need separate evaluation.
Underlying math
Formula
Each plotted curve = saturation pressure at given temperature for that refrigerant. For pure refrigerants and azeotropes: P_sat = f(T) single curve. For zeotropic blends: P_bubble = f(T) solid, P_dew = f(T) dashed.
Source
Saturation pressures from CoolProp 7.2.0 (Bell, Wronski, Quoilin, Lemort 2014, doi:10.1021/ie4033999), REFPROP-compatible Helmholtz EOS. For 11 manufacturer-blend refrigerants not in CoolProp's reference library, values from named manufacturer PT charts (Honeywell, Chemours, Arkema, AGC).
Worked example
R-410A vs R-32 vs R-454B at 95°F (typical residential design ambient): R-410A: 278 PSIG R-32: 296 PSIG (+6.5% vs R-410A) R-454B: 262 PSIG bubble / 256 PSIG dew (−5.8% vs R-410A) At 40°F (evaporator): R-410A: 119 PSIG R-32: 124 PSIG R-454B: 115 PSIG / 113 PSIG Interpretation: R-32 runs slightly higher pressure than R-410A; R-454B slightly lower. All three within standard 500 PSI service equipment ratings.
Related tools
PT Calculator
Single-refrigerant lookup, either direction.
Retrofit Compatibility
Structured pair comparison: lubricants, safety, pressure, glide, GWP.
R-410A detail page
Full reference + GWP + retrofit guidance.
R-454B detail page
Leading R-410A replacement (A2L).
Full Comparison Guide
Long-form sourced guide to all common HVAC refrigerant comparisons.
Frequently asked
›What does this tool show?
Pick 2-4 refrigerants and the tool overlays their saturation pressure-temperature curves on one set of axes. The result makes pressure-envelope comparisons across the operating range immediate — R-454B vs R-410A across residential AC, R-22 vs R-407C for retrofit, R-32 vs R-410A for new-equipment specification.
›Why are some curves dashed?
Solid lines are the bubble (saturated liquid) curve at the temperature given. Dashed lines are the dew (saturated vapor) curve. For pure refrigerants and azeotropes (R-22, R-32, R-134a, R-507A) the two coincide so only the solid line is drawn. For zeotropic blends (R-407C, R-454C, R-455A, R-448A, R-449A) both are shown and the vertical gap at any temperature is the temperature glide at that pressure.
›Why does my comparison look squished when I mix high- and low-pressure refrigerants?
If you include refrigerants with very different operating envelopes — R-744 (CO₂, 800+ PSIG at 70°F) with R-1234ze (~50 PSIG at 70°F) — the linear y-axis compresses lower-pressure curves toward zero. The relationship is still correct but visual readability suffers. For wildly different envelopes, do two separate comparisons (high-pressure family, low-pressure family) for cleaner reading.
›How do I compare two refrigerants for retrofit feasibility?
Retrofit feasibility depends on more than the PT curve: lubricant compatibility, component pressure rating, safety class change, capacity match, and glide all matter. The PT overlay shows whether system pressures will be comparable across the operating range (look at the curves at 40°F evaporator and 110°F condenser for residential AC; -20°F evap and 95°F cond for LT walk-in). For a structured pair comparison, use the Retrofit Compatibility Calculator.
›What are the typical use cases for PT comparison?
Five primary uses: (1) retrofit feasibility — R-22 vs candidate replacement (R-407C, R-422D, R-454C); (2) new-equipment specification — R-32 vs R-410A vs R-454B for residential AC; (3) commercial transition — R-404A vs R-448A vs R-449A vs R-454C for low-GWP commercial refrigeration; (4) mobile AC — R-134a vs R-1234yf compatibility; (5) phase-down trajectory visualization — showing pressure envelope evolution across a refrigerant family over decades.
›Does the chart account for service temperature ranges?
The chart spans -40°F to 130°F by default — covering the residential AC service range. For commercial refrigeration use the lower end (-40°F to 30°F evap, 80°F to 130°F condenser). For chillers focus on the 30°F-130°F band. For mobile AC focus on the 30°F-150°F band. The chart includes the full envelope but interpretive focus depends on application.
›What's the relationship between PT curve slope and operating efficiency?
Steep PT curves (high dP/dT) mean small temperature changes produce large pressure swings. R-32 is steeper than R-410A; R-744 (CO₂) is steeper than R-32 in its sub-critical regime. Steep curves require pressure-rated components and tighter charge control but offer higher volumetric capacity per unit displacement. Flatter PT curves (R-134a, R-1234yf) are forgiving but lower capacity.